code: def xy_toupvp(xc, yc):
      up = (4 * xc) / ((-2 * xc) + (12 * yc) + 3)
      vp = (9 * yc) / ((-2 * xc) + (12 * yc) + 3)
      return (up, vp)
  
file_path: vispy/examples/demo/gloo/galaxy/galaxy_specrend.py
imports: import math
label_desc: Use image node_id 2 for calling a global function with example usage: xy_toupvp(xc, yc) and returns: up,  vp